The computing speed of electromagnetic transient model for grid-connected photovoltaic power system is very slow because of its complexity. To solve this problem, a general electromechanical transient model for grid-connected photovoltaic power system is proposed, in which there are not electrical components and high frequency switching device, and it only consists of pure mathematic calculations, is simple and has fast calculation speed. By comparing the simulation results of this electromechanical transient model with electromagnetic transient model in PSCAD/EMTDC, we found that the simulation time is reduced greatly and the results are agreeable basically, which verifies the correctness and validity of the electromechanical transient model. The electromechanical transient model provides reference model for simulation and modeling of large scale grid-connected photovoltaic power station and is of great practical value.